JP6552233B2 - sewing machine - Google Patents

Description

  The present invention relates to a sewing machine for embroidery.

  The sewing machine sews while pressing the fabric with the foot. First, the presser foot suppresses the lifting of the cloth following the needle when the needle is pulled out of the cloth. Second, the presser foot holds the cloth together with the feed dog and feeds the cloth smoothly. In order to exert these functions effectively, it is necessary to appropriately control the pressing force exerted by the press foot on the cloth based on the thickness and flexibility of the cloth.

  The sewing machine entangles the upper thread and the lower thread to form a seam. If the seams become tight, highly elastic fabrics such as jerseys and knit fabrics will shrink, and if the seams are weak, the yarns will tend to loosen. Therefore, it is necessary to manage the tension (yarn tension) etc. of the yarn based on the thickness and stretchability of the fabric.

  In order to embroider the cloth, the cloth is held by the embroidery frame instead of the feed dog, and the cloth is horizontally and horizontally moved by the frame driving device. For this reason, when the sewing machine is used for embroidery, the presser foot is lifted from the cloth surface by a predetermined distance before the embroidery sewing operation to start the embroidery sewing operation (see, for example, Patent Document 1). In order to effectively exhibit the function of the presser foot in embroidery, it is necessary to appropriately manage the positional relationship between the presser foot and the fabric based on the thickness of the fabric.

  When embroidering on a highly elastic fabric such as a quilt, the actual height of the presser foot may be lower than the set distance of the presser foot to the fabric, which may cause sewing defects. Therefore, for a highly stretchable fabric, it is necessary to appropriately manage the positional relationship between the presser foot and the fabric based on the thickness and the amount of stretch of the fabric.

  Thus, conventionally, like the invention of Patent Document 1, the cloth thickness is detected, and the sewing conditions are set according to the cloth thickness. When the presser foot was lowered onto the fabric and the presser foot stopped without resisting the repulsive force of the fabric, the height of the presser foot at that time was regarded as the fabric thickness.

JP 2006-20757 A

  However, the fabric naturally has elasticity. If the stop height of the presser foot is the thickness of the cloth, the thickness of the cloth compressed by the presser foot is detected, and the thickness of the cloth at no load can not be detected. Also, the stretchability of the cloth varies depending on the cloth type. That is, the amount of compression of the cloth by the presser foot differs depending on the type of cloth, and the thickness of the cloth at no load can not be set based on the thickness after compression.

  Therefore, according to the conventional cloth thickness detection method, the sewing conditions can not be set according to the cloth thickness at no load, and it can not be said that the sewing quality and the embroidery quality are enhanced. On the contrary, when the difference between the actual thickness of the non-loaded cloth thickness and the conventional cloth thickness detection is large, the set sewing conditions may lead to a decrease in sewing quality and embroidery quality.

  The present invention has been proposed to solve the problems of the prior art as described above, and can detect the thickness and stretchability at no load of the cloth, and by setting the sewing conditions based on these thickness and stretchability. An object of the present invention is to provide a sewing machine capable of enhancing sewing quality and embroidery quality.

In order to achieve the above object, a sewing machine according to the present invention is provided with a presser foot mounted on the lower end of a presser bar supported so as to be vertically movable on a machine frame and pressing the presser foot as fabric. A press-up lever which can be moved up and down, an actuator which lowers the press-up lever by a predetermined amount to compress the cloth, and the actuator and the press-down foot are interposed between the press-up lever The spring body applies an urging force to the presser foot, which is compressed by the descent of the descent amount and offsets the repulsive force of the fabric, the encoder which detects the descent amount of the presser foot, and the presser foot compresses the fabric. still at two timings in the process of descending, based on the lowering amount of the encoder detects, e Bei and a calculator for calculating the thickness of the fabric, it said Starring The portion calculates the biasing force equal to the repulsive force from the amount of contraction of the spring body based on the predetermined amount of descent of the pressing lever and the amount of descent of the pressing foot, and the calculated biasing force is The height of the presser foot at the timing when it becomes zero is calculated, and the height of the presser foot calculated is taken as the thickness of the fabric, and the initial height Do of the presser foot and the spring constant of the spring are ks, The descent amounts dc (t1) and dc (t2) of the presser foot at two timings t1 and t2 and the swinging amounts do (t1) and do (t2) of the presser lever at two timings t1 and t2 Based on the following equation, two simultaneous equations having A and Lo as unknowns are generated and solved to obtain the thickness Lo of the fabric .
(Do−dc (t)) = A × [ks × (do (t) −dc (t))] + Lo

  The calculation unit calculates the shrinkage of the fabric at a predetermined timing from the thickness of the fabric and the height of the presser foot, and calculates the stretchability of the fabric from the biasing force of the spring body and the shrinkage of the fabric. You may

  A control unit may be provided to change sewing conditions based on at least one of the thickness and stretchability of the fabric.

  According to the present invention, the thickness and stretchability of the cloth at no load can be detected. Therefore, appropriate sewing conditions can be set, and the quality of the sewing product and the quality of the embroidery can be improved.

The structure of a sewing machine is shown, (a) is an external view, (b) is an internal block diagram. It is a figure which shows the detailed structure of a holding foot. It is a block diagram which shows the function structure of the computer with a built-in sewing machine. It is a schematic diagram which shows the force provided to a pressing foot, before a pressing foot contacts cloth. It is a schematic diagram which shows the force provided to a pressing foot in the compression phase of the cloth by a pressing foot. It is a time-series graph which shows descent | fall amount dc (t) of a pressing foot, and contraction amount ds (t) of a compression spring. It is a graph which shows the relationship between the height D (t) of a pressing foot and the repulsive force Fc. It is a flowchart which shows operation | movement of a control part and the cloth thickness calculating part.

(Overall configuration of sewing machine)
As shown in FIG. 1, the sewing machine 1 drops the needle 3 while pressing the cloth 100 placed on the needle plate 2 with the presser foot 8 and entangles the upper thread 200 and the lower thread 300 to form a seam. It is a household, professional or industrial device. The sewing machine 1 has a needle bar 4 and a hook 5. The needle bar 4 extends perpendicularly to the needle plate 2 and is attached so as to be vertically movable in the vertical direction. The needle bar 4 supports the needle 3 that holds the upper thread 200 at the tip of the needle plate 2 side. The kettle 5 has an internal hollow drum shape opened in one plane, is mounted horizontally or vertically with respect to the needle plate 2, and is rotatable in the circumferential direction. In the present embodiment, the hook 5 is mounted horizontally. The hook 5 accommodates a bobbin around which a lower thread 300 is wound.

  In the sewing machine 1, when the needle bar 4 moves up and down, the needle 3 passes through the cloth 100 with the upper thread 200, and when the needle 3 is raised, an upper thread loop is formed due to friction between the cloth 100 and the upper thread 200. Be done. Then, the upper thread loop is captured by the rotating hook 5 and the bobbin from which the lower thread 300 is fed passes through the upper thread loop as the hook 5 rotates, so that the upper thread 200 and the lower thread 300 become entangled, and the seam Is formed.

  The needle bar 4 and the hook 5 are driven by the common sewing machine motor 6 as a power source via respective transmission mechanisms. An upper shaft 61 extending horizontally is connected to the needle bar 4 via a crank mechanism 62. The rotation of the upper shaft 61 is converted into a linear motion by the crank mechanism 62 and transmitted to the needle bar 4 so that the needle bar 4 moves up and down. A horizontal shaft 63 is connected to the shuttle 5 via a gear mechanism 64. When the hook 5 is installed horizontally, the gear mechanism 64 is, for example, a cylindrical worm gear having an axial angle of 90 degrees. The gear mechanism 64 converts the rotation of the lower shaft 63 by 90 degrees and transmits it to the hook 5, whereby the hook 5 rotates horizontally.

  The upper shaft 61 is provided with a pulley 65 having a predetermined number of teeth. Further, the lower shaft 63 is provided with a pulley 66 having the same number of teeth as the pulley 65 of the upper shaft 61. Both pulleys 65 and 66 are connected by a toothed belt 67. When the upper shaft 61 rotates with the rotation of the sewing machine motor 6, the lower shaft 63 rotates through the pulleys 65 and 66 and the toothed belt 67. Thereby, the needle bar 4 and the shuttle 5 operate in synchronization.

  The presser foot 8 is attached to the tip of the presser bar 81 and faces the needle plate 2 through the cloth 100 placed on the needle plate 2. The presser bar 81 extends vertically toward the needle plate 2 and is provided in the sewing machine frame so as to be movable up and down in the bar axis direction. The presser foot 8 is capable of coming into and coming out of contact with the cloth 100 by moving the presser bar 81 up and down.

(Details of presser foot)
As shown in FIG. 2, the presser bar 81 uses a stepping motor 82 built in the sewing machine 1 as an actuator. The stepping motor 82 has a drive gear 83 on the rotation shaft. The drive gear 83 is in mesh with a double gear 84. The double gear 84 is an intermediate gear for reduction that coaxially integrates a large diameter gear and a small diameter gear, and the large diameter gear meshes with the drive gear 83.

  The small-diameter gear meshes with a cam disk 85 in which tooth teeth are arranged along the outer periphery. The cam disc 85 has a surface parallel to the axis of the pressing rod 81, and a radially expanding spiral cam groove 85a is formed in the surface. The cam groove 85a has the rotation center of the cam disk 85 as a spiral center. A driven projection 86a is fitted in the cam groove 85a.

  The driven projection 86 a is provided so as to protrude from the presser lift lever 86. The driven projection 86 a is regulated so as to be able to swing in parallel with the slidable direction of the pressing rod 81. The presser lift lever 86 is pivotally supported at one end, and extends at right angles to the presser bar 81 with the axis point at the base end toward the presser bar 81, and is connected to the presser bar 81 at the distal end.

  When the stepping motor 82 is driven, the cam disk 85 is rotated via the drive gear 83 and the double gear 84. Depending on the rotation direction of the cam disk 85, the cam groove 85 a to which the driven projection 86 a follows expands in the radial direction of the cam disk 85 or contracts in the radial direction of the cam disk 85. When the cam groove 85a expands in the radial direction, the driven protrusion 86a descends toward the needle plate 2, and when the cam groove 85a which the driven protrusion 86a follows shrinks in the radial direction, the driven protrusion 86a separates from the needle plate 2 To rise.

  When the follower projection 86a is lowered, the presser-lifting lever 86 swings down the connection point with the presser bar 81 about the base end, and the presser bar 81 is pushed down. When the driven projection 86a is raised, the presser-lifting lever 86 swings up the connection point with the presser bar 81 about the base end, and the presser bar 81 is pushed up.

  A flange 81a extending in the radial direction of the rod is formed in the middle of the pressing rod 81, and a compression spring 81b is fitted with the flange 81a as a seat surface. The tip of the presser-lifting lever 86 has a ring shape, and is fitted into the presser bar 81 to press the compression spring 81 b. The compression spring 81 b is set to have a high spring constant such that the compression spring 81 b is not reduced by the lowering force of the presser-lifting lever 86 when the presser foot 8 is in a floating state. Therefore, the presser bar 81 is pressed by the flange 81 a via the compression spring 81 b and lowered by the presser lifting lever 86.

  The presser bar 81 is formed with a flange 81 c that extends in the radial direction of the bar immediately above the tip of the presser lift lever 86. When the presser foot lifting lever 86 is swung up, the tip thereof pushes up the flange 81c, and the presser bar 81 ascends.

  The amount of lifting and lowering of the presser bar 81 can be detected by the encoder 87. The encoder 87 is composed of a photo interrupter and a long linear scale 87c. In the photo interrupter, the light emitting diode 87a and the phototransistor 87b are opposed to each other and fixed in position. The long linear scale 87c has slits in parallel in the longitudinal direction, and intervenes between the light emitting diode 87a and the phototransistor 87b. The long linear scale 87 c is fixed to a pressing rod holder fixed to the pressing rod 81 and extends in parallel with the vertical movement direction of the pressing rod 81.

  When the presser bar 81 moves up or down, the long linear scale 87c moves up or down in conjunction with the presser bar holding. As the encoder 87 counts the number of slits passing between the light emitting diode 87a and the phototransistor 87b, the amount of rise and fall of the pressing rod 81 is detected.

(Fabric thickness detection)
FIG. 3 is a block diagram showing a functional configuration of a computer that controls each configuration of the sewing machine 1. The computer 9 is incorporated in the sewing machine 1 and includes a CPU, a memory, a stepping motor 82 serving as a power source of the pressing rod 81, and a motor driver of the sewing machine motor 6 serving as a power source of other configurations of the sewing machine 1 It consists of an interface connected with 87. The computer 9 includes a control unit 91 and a cloth thickness calculation unit 92.

  The controller 91 outputs a pulse signal to the sewing machine motor 6 to drive each component of the sewing machine 1. Further, the control unit 91 outputs a pulse signal of a constant pulse interval to the stepping motor 82 to swing up or swing down the press-up lever 86 at a constant speed. Thus, the control unit 91 raises and lowers the presser foot 8 with respect to the cloth 100.

  The cloth thickness calculator 92 uses the presser foot 8 as a cloth thickness detection sensor, and calculates the thickness and stretchability of the cloth 100 when there is no load. FIG. 4 is a schematic diagram illustrating the force applied to the presser foot 8 before the presser foot 8 contacts the cloth 100. FIG. 5 is a schematic diagram showing the force applied to the presser foot 8 in the compression stage of the cloth 100 by the presser foot 8.

  As shown in FIG. 4, the control unit 91 rotates the stepping motor 82 at a constant speed. The press-up lever 86 is swung down by a swing amount do (t) equal to the rotation amount of the stepping motor 82. Before the presser foot 8 comes into contact with the cloth 100, all the swinging amount do (t) is directed to the presser foot 8, and the presser foot 8 is a descent amount do of the same amount as the rotation amount of the stepping motor 82. It descends at (t).

  As shown in FIG. 5, when the presser foot 8 starts pushing the cloth 100, the cloth 100 receives a repulsive force Fc. The compression spring 81b is compressed by the press-up lever 86 until the repulsive force Fc is canceled by the biasing force Fs. At this time, the press-up lever 86 is swung down by a swing amount do (t) that is the same amount as the rotation amount of the stepping motor 82. Of this swing amount do (t), the contraction amount ds (t) is the same. It is distributed to the contraction of the compression spring 81b, and the presser foot 8 is pushed down by the lowering amount dc (t). The descent amount dc (t) is detected by the encoder 87 as the number of slits.

  FIG. 6 is a time-series graph showing the descent amount dc (t) of the presser foot 8 and the contraction amount ds (t) of the compression spring 81b. As shown in FIG. 6, before the presser foot 8 comes in contact with the cloth 100, the presser foot 8 descends at a constant speed. When the presser foot 8 starts pressing the cloth 100 and the presser foot 8 continues to descend, the repulsive force Fc of the cloth 100 becomes strong according to the descent of the presser foot 8. Therefore, the compression spring 81b contracts so as to offset the repulsive force Fc, and gradually increases the contraction amount ds (t). On the other hand, the descent amount dc (t) of the presser foot 8 gradually decreases by the amount assigned to the contraction amount ds (t) and finally stops. At each time, the sum of the descent amount dc (t) and the contraction amount ds (t) is equal to the swing-down amount do (t).

  FIG. 7 is a graph showing the relationship between the height D (t) of the presser foot 8 and the repulsive force Fc (t). As shown in FIG. 7, the repulsive force Fc is zero until the presser foot 8 contacts the cloth 100. After the presser foot 8 contacts the cloth 100, the height D of the presser foot 8 decreases. The repulsive force Fc (t) increases. Assuming that the cloth 100 is a spring, the repulsive force Fc increases in proportion to the amount of depression of the presser foot 8.

Based on the above, after the contact of the presser foot 8 with the cloth 100, the relationship between the height D (t) of the presser foot 8 and the repulsive force Fc (t) is expressed by the following equation (1). A is a constant.
D (t) = A × Fc (t) + L o (1)

In the above equation (1), Lo is the height of the presser foot 8 when the repulsive force Fc is zero, that is, the thickness of the cloth 100 at no load. Then, since the repulsive force Fc and the biasing force Fs of the compression spring 81b always balance, assuming that the spring constant of the compression spring 81b is ks, and the contraction amount of the compression spring 81b at time t is ds (t), the above equation (1) Can be transformed into equation (2) below.
D (t) = A × (ks × ds (t)) + L o (2)

Here, the contraction amount ds (t) is the result of subtracting the descent amount dc (t) of the presser foot 8 from the swing amount do (t). Further, the height D (t) of the presser foot 8 is the result of subtracting the descent amount dc (t) of the presser foot 8 from the initial height Do before the start of the descent. Therefore, the above formula (2) can be rewritten as the following formula (3).
(Do−dc (t)) = A × [ks × (do (t) −dc (t))] + L o (3)

Since the initial height Do and the amount of swing down do (t) are known, and the amount of drop dc (t) of the presser foot 8 can be detected by the encoder 87, the spring constant ks of the compression spring 81b is measured in advance. If, unknowns are two of a and L o. Therefore, the thickness Lo of the non-loaded fabric 100 can be derived by measuring the descent amounts dc (t1) and dc (t2) of the presser foot 8 at two timings t1 and t2 different in time. it can.

The timing at which the presser foot 8 is in contact with the cloth 100 is timing tp, and the spring constant of the cloth 100 is kc. During the descent of the presser foot 8, the biasing force Fs and the repulsive force Fc balance each other. Since tp + t) is a difference between the amount of swing down do (tp + t) and the amount of decrease dc (tp + t), the following equation (4) is established. In Equation (4) below, since the unknown is only the spring constant kc, the spring constant kc can be obtained to make the fabric 100 stretchable.
ks × (do (tp + t) −dc (tp + t)) = kc × (dc (tp + t) −dc (tp)) (4)

  The cloth thickness calculation unit 92 receives the information of the pulse signal from the control unit 91 to the stepping motor 82, integrates the swing amount do (t) Δt per unit time, and the swing amount do (( The amount of swinging down do (t2) at t1) and timing t2 is calculated.

  Further, the cloth thickness calculation unit 92 receives the input of the number of slits from the encoder 87, integrates the number of slits, and decreases descent amount dc (t1) of the presser foot 8 at timing t1 and descent amount dc of the presser foot 8 at timing t2. Calculate (t2).

  Then, the cloth thickness calculation unit 92 generates simultaneous equations from the above equation (3), solves the simultaneous equations, and calculates the cloth thickness Lo when the cloth 100 is not loaded. In addition, the descent amount dc (tp) of the presser foot 8 at timing tp is calculated from the number of slits when the presser foot 8 comes in contact with the fabric 100 from the cloth thickness Lo, and the elasticity kc of the fabric 100 is calculated from the above equation (4). Calculate

  The number of slits per unit time is constant before the presser foot 8 contacts the cloth 100, and the number of slits per unit time is zero after the expansion limit of the cloth 100. Therefore, the cloth thickness calculation unit 92 monitors the number of slits, sets the timing t1 after the timing when the number of slits per unit time changes, and sets the timing t2 before the number of slits per unit time becomes zero. Then, various parameters for solving the simultaneous equations can be obtained with the timing t1 and the timing t2 as sufficiently different timings.

(Control based on cloth thickness detection)
The controller 91 outputs a pulse signal to the sewing machine motor 6 to drive each component of the sewing machine 1. The control unit 91 receives the information indicating the cloth thickness from the cloth thickness calculation unit 92, and drives the stepping motor 82 so that the presser foot 8 is grounded to the surface of the cloth 100 at the height at no load. Alternatively, the control unit 91 receives the information indicating the fabric thickness and the stretchability from the fabric thickness calculating unit 92, and drives the stepping motor 82 so that the presser foot 8 presses the fabric 100 at a predetermined pressure. Alternatively, the control unit 91 receives information indicating the fabric thickness from the fabric thickness calculation unit 92 and drives the stepping motor 82 so that the presser foot 8 is floated from the fabric 100 by a predetermined distance.

  Further, the control unit 91 receives information indicating the stretchability of the fabric 100 from the fabric thickness calculation unit 92, and adjusts the pulling or tone of the upper thread 200, the lowering or tone of the lower thread 300, or the sewing speed. Form tight seams that do not cause defects such as fabric shrinkage.

  Furthermore, the control unit 91 receives the information on the stretchability and thickness of the cloth 100, and determines the cloth type of the cloth 100. Then, the control unit 91 takes into consideration the type of cloth, and presses the presser foot 8, lifts the upper thread 200, tunes the upper thread 200, pulls down the lower thread 300, tunes the lower thread 300, sews the sewing speed, etc. Change the condition. At this time, for example, the sewing machine 1 can be provided with a CCD camera that recognizes the type of cloth, and the control unit 91 can use the judgment of the cloth type of the cloth 100 by image processing in combination.

(Operation)
The operations of the controller 91 and the cloth thickness calculator 92 are shown in the flowchart of FIG. The controller 91 lowers the presser foot 8 (step S01). When the descent of the presser foot 8 occurs, the cloth thickness calculation unit 92 records the swinging amount do (t) of the press-up lever 86 from the integral value of the pulse number of the pulse signal in time series. In addition, when the descent of the presser foot 8 occurs, the cloth thickness calculation unit 92 records the descent amount dc (t) of the presser foot 8 from the integral value of the number of slits in time series (step S02).

  The cloth thickness calculator 92 monitors the number of slits per unit time Δt, and when the number of slits per unit time Δt changes (Yes in step S03), the presser foot at the timing t1 after the unit time Δt from the change timing. 8 descent amount dc (t1) and swing-down amount do (t1) of the press-up lever 86 are calculated (step S04).

  In addition, when the number of slits per unit time Δt becomes zero (Yes in step S05), the cloth thickness calculation unit 92 lowers the holding foot 8 dc (t2) at the timing t2 before the unit time Δt from the change timing. Then, the swing-down amount do (t2) of the press-up lever 86 is calculated (step S06).

  Then, the cloth thickness calculator 92 generates an equation by substituting the descending amount dc (t1) and the swing-down amount do (t1) into the above equation (3) (step S07), and the descending amount into the above equation (3). Substitute dc (t2) and swing amount do (t2) to generate another equation (step S08), solve simultaneous equations, and calculate the unloaded thickness Lo of the cloth 100 (step S09) .

  Furthermore, the cloth thickness calculation unit 92 calculates the descent amount dc (tp) of the presser foot 8 at the timing tp at which the presser foot 8 descends to the cloth thickness kc (step S10). Then, the descent amount dc (tp), the swing-down amount dc (t1) and the descent amount dc (t1) are substituted into the above equation (4) to solve the equation to obtain the elasticity kc of the cloth 100 (step S11).

(Action effect)
As described above, the sewing machine 1 causes the presser foot 8 for pressing the cloth 100 to move up and down with respect to the cloth 100 by the push-up lever 86 to compress the cloth 100. The press-up lever 86 is lowered by a constant lowering amount by an actuator such as a stepping motor 82. A spring body such as a compression spring 81 b is interposed between the actuator and the presser foot 8. A part of the fixed lowering amount of the press-up lever 86 is distributed and contracted, and the spring body applies an urging force Fs to the presser foot 8 to offset the repulsive force Fc of the cloth 100.

  Then, the amount of descent of the presser foot 8 is detected by the encoder 87, and the thickness of the cloth 100 is calculated by the cloth thickness calculator 92. The cloth thickness calculator 92 calculates based on the number of command pulses for the stepping motor 82 and the detection value of the encoder 87 at two timings while the presser foot 8 compresses the cloth and is still descending.

  Thereby, the thickness at the time of no load of cloth can be detected with sufficient accuracy. Therefore, appropriate sewing conditions can be set, and the quality of the sewing product and the quality of the embroidery can be improved. The pressing rod 81 is suspended by, for example, a tension spring so that the compression spring 81b has a high response to the repulsive force Fc, and the spring constant of the tension spring is set to be slightly smaller than the spring constant ks of the compression spring 81b. You may The actuator is not limited to the stepping motor 82, and any known actuator that can move the presser bar 81 up and down may be applied. For example, it may be a linear motor which directly moves the presser bar 81 up and down.

  The cloth thickness calculation unit 92 calculates the biasing force Fs, which is equal to the repulsive force Fc, from the amount of contraction of the spring body based on the fixed descent amount of the press-up lever 86 and the descent amount of the presser foot 8. The height of the presser foot 8 was calculated at the timing at which Z became zero, and the calculated height of the presser foot 8 was taken as the thickness of the cloth 100.

  For example, it is theoretically possible to detect the thickness of the cloth 100 when there is no load by detecting the timing when the descending amount of the presser foot 8 changes, but the repulsive force Fc of the cloth 100 is small. Therefore, it is difficult to identify a clear change point. On the other hand, according to the sewing machine 1, since the thickness of the cloth 100 is calculated using the known biasing force Fs of the spring body instead of the repulsive force Fc of the cloth 100, it is simple and highly accurate.

  Further, the cloth thickness calculation unit 92 calculates the shrinkage of the cloth 100 at a predetermined timing from the thickness of the cloth 100 and the height of the presser foot 8, and the elasticity kc of the cloth 100 from the biasing force Fs of the spring body and the shrinkage of the cloth Fc. Was calculated. Thereby, the thickness and stretchability at no load of the cloth can be detected with high accuracy. Therefore, appropriate sewing conditions can be set, and the quality of the sewing product and the quality of the embroidery can be improved.

(Other embodiments)
Although the embodiments of the present invention have been described as above, various omissions, replacements, and changes can be made without departing from the scope of the invention. And this embodiment and its modification are included in the range and the gist of invention, and are included in the invention indicated to the claim, and its equivalent range.

  For example, in order to detect the thickness and stretchability of the cloth 100, processing of laser measurement or image determination may be used in combination. By attaching a laser measuring instrument to the presser foot 8 and measuring the approaching distance of the presser foot 8 to the cloth 100, the grounding of the presser foot 8 to the cloth 100 is detected, and the cloth from the height of the presser foot 8 is detected. Determine the thickness of 100. Further, a CCD camera that captures the positional relationship between the presser foot 8 and the cloth 100 is attached to the sewing machine 1, the grounding of the presser foot 8 to the cloth 100 is detected by image processing, and the thickness of the cloth 100 is determined from the height of the presser foot 8. Determine

1 sewing machine 2 needle plate 3 needle 4 needle bar 5 hook 6 sewing machine motor 61 upper shaft 62 crank mechanism 63 lower shaft 64 gear mechanism 65 pulley 66 pulley 67 toothed belt 8 presser foot 81 presser bar 81a flange 81b compression spring 81c flange 82 stepping Motor 83 Drive gear 84 Double gear 85 Cam disk 85a Cam groove 86 Press up lever 86a Followed projection 87 Encoder 87a Light emitting diode 87b Phototransistor 87c Long linear scale 9 Computer 91 Control unit 92 Cloth thickness calculation unit 100 Cloth 200 Upper thread 300 Lower thread

Claims (3)

A presser foot attached to a lower end of a presser bar supported vertically movably on a sewing machine frame and pressing a fabric to be sewn;
A press-up lever that allows the presser foot to move up and down with respect to the fabric;
An actuator that compresses the fabric by lowering the press-up lever by a constant lowering amount;
A spring body interposed between the actuator and the presser foot, which is contracted by the downward movement of the presser lever to apply a biasing force to the presser foot to offset the repulsive force of the fabric;
An encoder for detecting the amount of descent of the presser foot;
A computing unit that computes the thickness of the fabric based on the amount of descent detected by the encoder at two timings in which the presser foot compresses the fabric and at the same time descents;
Bei to give a,
The arithmetic unit is
The biasing force equal to the repulsive force is calculated from the contraction amount of the spring body based on the constant lowering amount of the presser lifting lever and the lowering amount of the presser foot,
Calculate the height of the presser foot at the timing when the calculated urging force becomes zero,
The calculated height of the presser foot is the thickness of the fabric,
The initial height Do of the presser foot, the spring constant of the spring body as ks, and the descent amounts dc (t1) and dc (t2) of the presser foot at two timings t1 and t2, and the two at the two timings t1 and t2. Based on the swing amount do (t1) and do (t2) of the presser lever, two simultaneous equations in which A and Lo are unknowns are generated and solved from the following equation to obtain the thickness Lo of the fabric,
(Do−dc (t)) = A × [ks × (do (t) −dc (t))] + Lo
A sewing machine characterized by The arithmetic unit is
Calculate the shrinkage of the fabric at a predetermined timing from the thickness of the fabric and the height of the presser foot,
Calculating the stretchability of the fabric from the biasing force of the spring body and the shrinkage of the fabric;
Claim 1 Symbol placement of the sewing machine characterized by. A control unit for changing sewing conditions based on at least one of the thickness and stretchability of the fabric;
The sewing machine according to claim 2, wherein:

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